Device comprising an electric discharge tube having a liquid cathode



Sept. 22, 1953 T. DoUMA 2,653,278

l DEvICE CoMPEIsINC AN ELECTRIC DISCHARGE TUBE HAVING A LIQUID CAIHCDE Filed June 13, 1951 -fE---g---AE-f INVENTOR TJISKE DouMA BY w AGENT Patented Sept. 22, 1953 i DEVICE COMPRISING AN ELECTRIC DIS- CHARGE TUBE HAVING A LIQUID CATHODE Tjiske Douma, San Carlos, Calif., assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application June 13, 1951, Serial No. 231,332 In the Netherlands June 30, 1950 This invention relates to devices comprising an electric discharge tube having a liquid cathode and at least two capacitive ignition electrodes.

In discharge tubes of known type having a liquid cathode and more than one capacitive ignition electrode, the ignition electrodes are, as a rule, connected in parallel. Since the ignition electrodes can be made identical only with diiculty, the position is usually such that one of the ignition electrodes only is operative untilY it becomes defective, whereupon it is switched oi by means of a fuse. The total life of the tube is in this case not longer than the sum of the lives of the ignition electrodes so used.

For many uses and more particularly for devices intended for high-frequency heating, the short lives of tubes having a capacitiveignition electrode is a serious inconvenience, more particularly7 because other types of tubes suitable for this purpose have short lives or unsatisfactory outputs.

The object of the invention is to mitigate the said disadvantages.

According to the invention, a device comprising an electric discharge tube having a liquid cathode and at least two capacitive ignition electrodes, is characterized in that the ignition electrodes are used in such manner that two sequena plurality of ignition electrodes, so that the mean temperature of the ignition electrodes is lower than if only one ignition electrode were used in the tube with the same load. Consequently, itis 4 desirable that the ignition electrodes should not be arranged too closely to one another and for this purpose a spacing of about 1 cm. with a.

4 Claims. (Cl. 315-336) Vto the vicinity of the arc produced is divided over thickness of the ignition electrodes of some millimetres is suicient. Preferably, use is made of at least four ignition electrodes operable in cyclic sequence.

The invention will now be explained more fully by reference to the accompanying diagrammatic drawing, given by way of example, showing an electric discharge tube I vhaving a liquid cathode 2 and a liquid anode 3. Provided in the cathode are ve capacitive ignition electrodes 4, each constituted by a molybdenum pin provided in the bottom of the tube and covered with glass having a low dielectric loss. Reference numeral 5 indicates an ignition-voltage source comprising a device for supplying the ignition pulses to the ignition electrodes 4 in cyclic sequence. The load on the tube is constituted by anr inductor 6 and a capacitor l, which jointly constitute a damped oscillatory circuit fed from a direct-voltage source 8.

What I claim is:

1. Av vapor discharge device comprising an electric discharge tube having a liquid cathode and a plurality of spaced capacitative ignition electrodes, means to generate ignition pulses, and means to sequentially connect each of said ignition electrodes to said pulse generating means.

2. A device as claimed in claim 1 in which the spacing between adjacent ignition electrodes is greater than their thickness.

3. A device as claimed in claim 2 in which the tube has at least four ignition electrodes.

4. A device as claimed in claim 1 in which the ignition electrodes are operated in cyclic sequence.

TJISKE DOUMA.

References Cited in the file of this patent UNITED STATES PATENTS 0 Number Name Date 2,398,422 Germeshausen Apr. 16, 1946 2,495,831 Warmoltz Jan. 31, 1950 2,533,095 Cox Dec. 5, 1950 

